I have seen neuer Wein (new wine) going by different names in different parts of Germany over thirty-some years. I thought I originally saw it called Neuewein, as one word, but maybe not, and I agree that neuer Wein would be grammatically correct.
Anyway, I first read about Neuer Wein before my first "my-dime" trip to Germany in 1988. I read that it was served in the fall with Zwiebelkuchen (onion tort). I first had Zwiebelkurchen, without neuer Wein, in a cafe in Ulm, about 4 days into my 1988 trip. It was early September, so maybe a bit early for neuer Wein.
Later, on my last full day in Germany on that trip, we traveled from Lahr to Mainz and had a change of trains in Heidelberg. Outside the restaurant in the Heidelberg Hbf (back then they had real sit-down restaurants in train stations, not the fast food courts of today) was a board advertising "neuer Wein and Zwiebelkuchen". I tried to order it, and the waiter informed me that I couldn't get it because it was Sunday.
I was stunned. A German restaurant not serving wine on Sunday. Then I realized, no, it was not the wine I couldn't buy on Sunday. Back then the bakeries were not open on Sundays, and they wouldn't serve Zwiebelkuchen that wasn't freshly baked that day.
Since then I've seen it called neuer Wein in Weikersheim in 2007 and Federweiss in Cochem in 2008. I also saw it called something else in Bad Wildbad, in the Schwarzwald, in 2017. I think it was "Traubenmost".
I think neuer Wein (or Federweiss) tastes a little like hard apple cider, very fruity, and fizzy.
Oh, yeah, and I had Käsespätzle in Zell (Mosel) in 2008.